software control systems for smart antenna

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308

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Volume: 04 Issue: 11 | Nov-2015, Available @ http://www.ijret.org 164

SOFTWARE CONTROL SYSTEMS FOR SMART ANTENNA

Aatish Gandotra1 , Tejaswi Singh

2

1Student, Electronics and Communication Engineering, Guru Tegh Bahadur Institute of Technology, Delhi, India

2Student, Computer Science Engineering, Guru Tegh Bahadur Institute of Technology, Delhi, India

Abstract A PCB containing microcontroller provides suitable DC voltages to the phase shifters and generates the smart antenna array

beam steering. The detected WiFi signals are transferred into a mobile device through a WiFi adapter. This chapter will focus

on the software design to automatically control the complete smart antenna array system. Since two microcontrollers

PIC18F4550 and LPC1768 are used to build control PCBs. There are also two specifically designed software programs

developed in order to configure the individual PCB. For the PIC18F4550, a graphical user interface (GUI) was developed to

communicate between a laptop and the control PCB. The GUI sends commands to a Microchip compiler called MPLAB and

transfers the control C code into a Hexadecimal (Hex) document. Through the Bootloader program, this Hex code will be

copied into the microchip PIC18F4550 and then configures the digital potentiometers to generate variable output voltages. A

script using VB is made to link all of the control steps automatically.

Key Words: Software Control System, Smart Antenna, Manual Control, Switching Control, Automatic Control.

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1. INTRODUCTION

Several improved versions of the GUI are investigated for

the LPC1768 control PCB. By utilizing the microcontroller

LPC1768, it is able to achieve the real time control, which

means there is no need for the Bootloader program again

after initialization. Due to the advantage of LPC1768, two

advanced GUIs have been implemented. Both of the GUIs

allow the user to detect service set identity (SSID) and

received signal strength indicator (RSSI) of WiFi signals

surrounding the mobile device. The basic GUI is able to

manually configure the digital potentiometers and display

the WiFi information. The control signals are transformed

from GUI to a virtual COM port, which is established by the

FT232RL, and directly go into the microcontroller. By

varying the phase shifter, the beam direction of the antenna

array could be changed in order to analyze and optimize the

signal strength of the received WiFi signals. Moreover, this

chapter provides beta version of an advanced software

package, which performs a basic smart antenna adaptive

beamforming.

There are mainly four sections in this chapter. Section 1.1

presents the software implementation introduction. GUI

designs for PIC18F4550 and LPC1768 are demonstrated in

Section 1.2 and Section 1.3, respectively. Finally, Section

1.4 summarizes this chapter.

1.1 Software Implementation for P1C18F4550

Control System

Figure 1.1 presents the block diagram of software

implementation using PIC18F4550 microcontroller.

Figure 1.1: Functional Block Diagram for PIC18F4550

The software control system is generally comprised of three

parts, as illustrated in Figure 1.1. Part I contains the main

algorithm to configure the microchip and digital

potentiometers, which simulates the SPI communication.

The program is made in C language and compiled in Dev-

C++ [2]. Then the C code is transferred into microchip C

language to set correct configuration bits, suitable I/O ports

and accurate delay time. Finally, MPLAB compiles the

program again and generates a hexadecimal document

which could be recognized by the microchip. Part II in the

software design is the Bootloader program with the function

of communicating between laptop and microcontroller

PIC18F4550. After initialization (discussed in Chapter 5),

the hexadecimal code generated by MPLAB is transferred

through Bootloader into the microchip. Finally, Part III is a

GUI designed in VC++ for Windows system. The GUI

provides two control methods for the phase shifter: manual

control and switching control. In the manual control, some

specific values will be sent to the digital potentiometers and

generate particular DC voltages. While in the switching

control, the output voltages are in square waves. This GUI

is used for briefly evaluating the digital potentiometers

and phase shifters. More advanced control method will be

demonstrated using microchip LPC1768.


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1.1.1 Programed PIC18F4550

There are three programs in PIC18F4550: SPI

communication, manual control and switching control.

These C codes have been evaluated in Dev- C++. Dev-

C++ is an integrated development environment (IDE)

distributed under the GNU general public license for

programming in C and C++. It is bundled with MinGW, a

free compiler. The IDE is written in Delphi.

1.1.1.1 SPI Communication

A virtual SPI communication has been established between

microcontroller PIC18F4550 and digital potentiometer

AD5290. The algorithm is based on the potentiometer’s

timing diagram.

Figure 1.2: Digital Potentiometer AD5290 Timing Diagram

[132]

PIC18F4550 controls three signal lines for these digital

potentiometers: CLK, and SDI. Clean transitions are needed

by the positive edge sensitive CLK input to avoid clocking

incorrect data into the serial input register. When is low,

the potentiometer loads data into the serial register on each

positive clock edge and the MSB of the 8-bit serial is loaded

first. The data setup and data hold times determine the valid

timing requirements. After eight clock cycles, the 8-bit

serial input data register transfer the words to the internal

RDAC register and the line returns to logic high. Extra

MSB bits will be ignored.

There are two methods to configure the potentiometers:

manual control and switching control.

1.1.1.2. Manual Control

In manual control, it is able to control digital potentiometer

to generate specific voltage levels to the phase shifter. An

example code showing configure only one potentiometer

using C in Dev- C++ is as follows:

#include <conio.h>

void init();

void write_byte(uchar data);

int CLK, dout[8], cs_bar;

void init()

{ cs_bar=1;

CLK=0; }

{ uint i,t;

for (i=1;i>0;i--)

{ init();

write_byte(0xfb);//11111011,251

}

for(t=0;t<8;t++)

{ printf("%d",dout[t]); }

getch();

return 0; }

void write_byte(uchar data)

{ uint i;

uchar temp;

cs_bar=0;

for (i=0;i<8;i++)

{

CLK=0;

temp=data&0x80;

if (temp==0x80)

dout[i]=1;

else

dout[i]=0;

CLK=1;

}

data=data<<1; }

cs_bar=1; }

This program is exactly following the timing diagram

provided in Figure 1.2. The purpose of this code is to write

an 8-bit data into the microcontroller and then transfer the

data into a digital potentiometer bit by bit on positive clock

cycle. The delay time is ignored to simplify the program. If

a number 251 is written into the microchip PIC18F4550, its

output to the digital potentiometer should be “11111011”. A

Printf function is added into the C code, so the result of

1111011 is showing on the screen, as presented in Figure

1.3.

Figure 1.3: C Code Result for SPI Communication

From the results in Figure 1.3, the virtual SPI

communication has been successfully established between

PIC18F4550 and the digital potentiometers. The algorithm

is fully matching the timing diagram. Then, the C code is re-

written in MPLAB to configure the microchip I/O ports.

MPLAB integrated development environment (IDE) is an

integrated toolset for development of embedded applications

employing Microchip's PIC and dsPIC microcontrollers [1].


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The following example demonstrates using PIC18F4550

configure only one potentiometer in MPLAB.

#include<p18f4550.h>

// Include the 18f4550 head file

#define REMAPPED_RESET_VECTOR_ADDRESS

0x1000 // Memory from 0x1000

#define cs_bar LATCbits.LATC1 // Set PIN RC1 as

#define dout LATAbits.LATA0 // Set PIN RA0 as output

data

#define CLK LATCbits.LATC2 // Set PIN RC2 as CLK

extern void _startup (void); // Set start up

#pragma code REMAPPED_RESET_VECTOR =

REMAPPED_RESET_VECTOR_ADDRESS

void _reset (void)

{ _asm goto _startup _endasm }

#pragma code // Set the suitable

configuration bits

void delay(uint x);

void init();

void write_byte(uchar data);

void delay(uint x) // Make a delay function

{ uint a,b;

for(a=x;a>0;a--)

for(b=275;b>0;b--); } // After simulation, x represent x

milliseconds

void init()

{ TRISAbits.TRISA0=0; // Set PIN RA0 as an

output, for the output data TRISCbits.TRISC1=0; // Set

PIN RC1 as an output, for TRISCbits.TRISC2=0; // Set

PIN RC2 as an output, for CLK

cs_bar=1; // Before data transfers, should be

logic high

CLK=0; } // Initialise the clock signal

void main()

{ uint i;

for (i=1;i>0;i--) // Run the main function once

init();

write_byte(0x84);//10000100,132 }//Write 132 into the

microcontroller’s memory

void write_byte(uchar data)

{ uint i;

uchar temp;

cs_bar=0; // Data starts to transfer, should be

logic low

Nop(); // Make a delay for

for (i=8;i>0;i--) // 8-bit data needs the transfer

function 8 times

{ CLK=0; // CLK goes to low to simulate a

clock signal

temp=data&0x80; // Check this bit is 0 or 1

if (temp==0x80) // If this bit is 1

dout=1; // The output data should be set as logic high

else // If this bit is 0

dout=0; // The output data should be set as logic low

Nop(); // Wait for the data processing

CLK=1; // CLK returns to high to finish a clock

cycle

Nop(); // Wait for the clock signal

data=data<<1; } // Left shift the data to write next bit into

the memory

CLK=0; // After data transfers, CLK

returns to 0

cs_bar=1; //After the function runs for

eight times,

// all of the eight bits have been

// transferred into the memory,

} // returns to high and finish the write_byte

function

Some I/O ports of PIC18F4550 are utilized as , CLK, and

SDI signals to simulate the SPI communication. In the code,

data 132 is transferred into the digital potentiometer.

In MPLAB, after compiling, the code is translated into a

hexadecimal document. Bootloader program is used to send

the “.hex” file into PIC18F4550. After resetting the control

PCB, a voltage of 15.47V is measured at the terminal W of

the digital potentiometer, which could configure the phase

shifters in the smart antenna array.

Figure 1.4: Measurement Result of PIC18F4550 Manual Control

Figure 1.4 illustrates the measurement of PIC18F4550

manual control for single digital potentiometer, which

matches the calculation. Then the algorithm is extended to

configure all of the sixteen digital potentiometers together

on the control PCB. Finally the PIC18F4550 manual

control program will work with the manual control GUI to

control the smart antenna array beam steering.

1.1.1.2. Switching Control

In switching control, the target is to generate square

waveforms from the digital potentiometers, as presented in

Figure 1.5.

Figure 1.5: Square Waveforms from Switching Control


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The fundamental algorithm is similar to the manual control,

however, in this implementation, the delay time is very

important. In the microchip C code, a delay time has been

added after sending the 8-bit values and a for-loop is

included in the main function to judge the delay time.

void delay(uint x)

{ uint a,b;

for(a=x;a>0;a--)

for(b=275;b>0;b--);}

The value of b determines the accuracy of delay time, which

has been simulated in MPLAB, as illustrated in Figure 1.6.

Figure 1.6: Delay Time Simulation in MPLAB

In Figure 1.6, several breakpoints (Red B) are set at the

beginning and end of the delay function. The Stopwatch in

MPLAB is used to observe the running time. After

simulations and optimizations, the value of b is set at 275

and x equals to 1. The program will run for 1 millisecond

(Red cycle), and later by controlling the value of x, the

required milliseconds can be achieved.

The simulated delay time function has been added into the

switching control main code and transferred into the

microcontroller PIC18F4550. Figure 1.7 demonstrates the

measured results by an oscilloscope. In this code, the DC

voltage is switching between 0 and 12V with a delay time of

9 milliseconds.

Figure 1.7: Measured Result of the Switching Control

1.1.2 Graphical User Interface for PIC18F4550

A graphical user interface is built to automatically configure

the PIC18F4550 control PCB.

Figure 1.8 shows the communication loop between GUI and

microchip.

Figure 1.8: Control Loop between GUI and Microchip

The control commands from GUI will automatically

generate a C code. MPLAB transfers the C code into a

hexadecimal document which will be sent into the

microchip through Bootloader. Finally the microcontroller

configures the digital potentiometers to provide suitable DC

voltages to the phase shifter in smart antenna array.

Figure 1.9 shows the GUI main interface for PIC18F4550.

Two control methods are provided according to the

algorithm described in Section 1.2.1.

Figure 1.9: GUI Main Window for PIC18F4550

1.1.2.1 Manual Control

The GUI is made using Microsoft Visual Studio 2010 [138],

which is a commercial integrated development environment

(IDE) product engineered by Microsoft for the C, C++, and

C++/CLI programming languages. In this software program,

the main section is written in C++.

The manual control interface is illustrated in Figure 1.10.

Figure 1.10: Manual Control GUI for PIC18F4550


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In manual control GUI, there are sixteen sliders to control

the digital potentiometers, with the voltage level from 0V to

30V in the precision of 0.1V. The scale is above the slider

and there stands a number showing the position. By using

the scales and sliders, it is able to configure the digital

potentiometers quickly and accurately. The text boxes are on

the right demonstrating the output voltages. The required

voltage of the phase shifter is from 0V to 13V, which can be

fully covered by this implementation. After pressing the

Generate button, a script written in VB will send these

sixteen voltage values into a predefined C code. Then

MPLAB reads this C code, compiles the program and

transfers it into a hexadecimal file. Finally, Bootloader

burns the hex document into the microcontroller

PIC18F4550 and control the digital potentiometers. By

using the manual control GUI, it is able to manually

configure the phase shifters in the smart antenna array and

estimate the beam steering.

1.1.2.2 Switching Control

In switching control, the digital potentiometers will generate

square waveforms to the phase shifters and the main beam

of the smart antenna will switch just between two directions.

It is a basic evaluating method for the smart antenna array.

Figure 1.11 shows the output waveforms. The voltage levels

are different but they share an identical switching period.

The software interface is displayed in Figure 1.12.

Figure 1.11: Output Square Waveforms

Same as the manual control, for the square waveform, the

voltage range is from 0V to 30V with a precision of 0.1V.

There are scales and positions of the sliders added into the

GUI to achieve the accurate control. Furthermore, in this

switching control application, the delay time has been added

into the design to setup a switching period. Also, a script is

made to automatically link the GUI to MPLAB, Bootloader

and PIC18F4550.

Figure 1.12: Switching Control GUI for PIC18F4550

Based on research and investigation, it is noted that

PIC18F4550 is difficult to achieve the real time control,

which means the Bootloader program cannot be ignored

during the control loop. The script built in the GUI is able to

generate an automatic control but each command requires a

long data transfer period and the program is not stable. The

basic control methods (manual control and switching

control) have already made the algorithms complicated. So

the GUI of PIC18F4550 is only used to generally estimate

the digital potentiometers and the phase shifters. More

advanced software programs are developed using the

microcontroller LPC1768.

1.2 Software Implementation for LPC1768 Control

System

1.2.1 Programme LPC1768

Figure 1.13 shows the block diagram for programming

LPC1768. The microchip control code is written in C

language and compiled by an online compiler provided by

mbed, as illustrated in Figure 1.14. The compiler generates a

binary document. A DOS based program transfers the binary

file into a hexadecimal code. Flash Magic burns the .hex file

into the microcontroller LPC1768, as demonstrated in

Figure 1.15 and Figure 1.16. Flash Magic is a PC tool for

programming flash based microcontrollers from NXP

utilizing a serial protocol [3]. An ISP programmer is

communicating between laptop and control PCB.


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Figure 1.13: LPC1768 Programming Block Diagram

Figure 1.14: LPC1768 Online Compiler

Figure 1.15: LPC1768 BIN to HEX Transformer

Figure 1.16: Flash Magic to Program LPC1768

Compared to PIC18F4550, the microchip LPC1768 is more

advanced. After initializing the microcontroller, as shown in

Figure 1.13, the compiler, transformer, flash magic and ISP

programmer are not required in the final communication.

When the configuration bits and algorithms have been setup

correctly, the LPC1768 will generate a virtual COM port (by

the FT232RL chip), which can be recognized by a terminal

emulator named Tera Term [140]. The GUI for LCP1768

can directly control the digital potentiometers through Tera

Term. It is able to achieve the real time control. The

communication block diagram for LPC1768 is presented in

Figure 1.17.

Figure 1.17: Real Time LPC1768 Communication Block

Diagram

Similar to PIC18F4550, the LPC1768 also controls the

digital potentiometers using virtual SPI communication, and

with the same algorithms in Section 1.2.1.

1.2.2 Graphical User Interface for LPC1768

There are also two GUI developed for LPC1768: Manual

Control and Automatic control. Both of the software

programs are able to detect service set identity (SSID) and

received signal strength indicator (RSSI) of WiFi signals

surrounding the laptop.

The GUI software can be installed on a computer with the

following minimum requirements:

• PC Compatible with Windows XP/7/Vista/ 8 – 32 or 64

bit

• At least 2 free USB Ports

Usually Windows 7 and later versions will recognize the

LPC1768 microcontroller automatically and there will be no

need to install the drivers. However, for previous Windows

version, two drivers for FT232RL microchip and the WiFi

adapter are required to be installed.

1.2.2.1 Driver Installation

The driver for LPC1768 has been written into FT232RL

microchip and the program will automatic start when the

USB port is connected to a PC running Windows. Figure

1.18 presents the steps to install the FT232RL.


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(a) (b)

( c ) ( d )

( e ) ( f )

( g ) ( h )

Figure 1.18: FT232RL Diver Installation

FT232RL provides a USB serial port which can be

recognized by Windows system. The laptop communicates

to LPC1768 through FT232RL USB to UART.

The installation steps for WiFi adapter are illustrated in

Figure 1.19.

( a ) ( b )

( c ) ( d )

( e ) ( f )

( g ) ( h )

Figure 1.19: WiFi Adapter Driver Installation

After installation, the WiFi adapter will replace the laptop’s

original WiFi antenna and the smart antenna array will be

used to detect WiFi signals around the laptop. The following

sections will focus on the GUI design to configure the smart

antenna array beam steering.


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1.2.2.2 Manual Control

As discussed in Section 1.3.1, the GUI sends the control

commands into Tera Term and then directly transfers to the

microprocessor LPC1768. Figure 1.20 presents the Tera

Term software which makes LPC1768 a virtual COM port

to the laptop.

( a ) ( b )

Figure 1.20: Tera Term Connection Setup

Figure 1.21: Manual Control GUI Start Screen for

LPC1768

Figure 1.21 presents the GUI start screen developed for

microprocessor LPC1768. This software program is written

in VC++ and C#. After clicking the Basic SmartWiFi

button, the main interface will appear, as displayed in Figure

1.22.

Figure 1.22: Manual Control GUI Main Screen for

LPC1768

In the upper right corner, there is a drop down menu item to

select the wireless adapter for evaluation. In the smart

antenna array system, an EDUP wireless adapter is used in

the implementation. So in the menu, “EDUP IEEE 802.11

b+g USB Adapter – Packet Scheduler Miniport” is

selected.

Figure 1.23: Wireless Adapter Selection for LPC1768

There are generally three sections in the software design. On

top is the main window showing MAC Address, SSID,

RSSI, Channel, Vendor, Privacy, Max Rate, Network Type

and Detected Time for all of the WiFi signals around a

laptop, as demonstrated in Figure 1.24.

Figure 1.24: WiFi Information of the GUI for LPC1768

On the bottom right, a window is drawing all of the real time

signal strength curves (in dBm) for the WiFi signals (as

shown in Figure 1.25(a)). Another tab in this window

illustrates the signal amplitudes in different channels.

( a ) ( b )

Figure 1.25: (a) WiFi Signal Strength Real Time Curve

(b) WiFi Signal Strength in Different Channels

On the bottom left, there exist eight real time sliders

controlling the eight Hittite analogue phase shifters on the

smart antenna board.

Figure 1.26: Real Time Control Slider for LPC1768


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By changing the voltages to the phase shifters, the main

beam direction of the antenna array is rotated, which

generates a variation of the received RSSI in the manual

control GUI. Figure 1.27 shows the evaluated results.

Different voltage levels are provided to the antenna array

and the received WiFi signal strength curves are able to

reflect the diversity.

Figure 1.27: Manual Control Evaluating Results for

LPC1768

1.2.2.3 Automatic Control

An improved version of the GUI has been developed which

can provide the smart antenna array automatic control. The

main screen is illustrated in Figure 1.28.

Figure 1.28: Automatic Control GUI for LPC1768

Figure 1.29: Antenna Array and WiFi Adapter Selection

In the current smart antenna array implementation, the four-

element linear antenna array with Archimedean spiral slots

is used. In Figure 1.29, the “4 Element Linear Antenna

Array” and “EDUP 802.11 b+g USB adapter” should be

selected. This automatic GUI is also compatible with more

elements antenna arrays. By selecting the EDUP USB

adapter, the original WiFi card of the laptop will be

disabled. The smart antenna array will detect and monitor

the WiFi signals for the control laptop.

Figure 1.30: Current Connected WiFi Information

On the bottom left of the advanced GUI, the current WiFi

information is displayed, as shown in Figure 1.30.

Furthermore, in the software program, some information

windows help to describe RSSI and Link Quality, as

illustrated in Figure 1.31 and Figure 1.32, respectively.

Figure 1.31: RSSI Description

RSSI is the relative received signal strength in a wireless

environment, in arbitrary units.

Figure 1.32: Link Quality Description

Link Quality is calculated from the correlation value

obtained when code lock is achieved between the local PN

code and the incoming PN codes.

There are three functions included in the Advanced GUI for

LPC1768: Scanning, Best Signal and Choose WiFi.

1.2.2.3.1 Scanning Function

Scanning: In scanning mode, the program enables scanning

of the surrounding environmental for WiFi signals. This

takes place by steering the main beam of the smart antenna

array


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Figure 1.33: Scanning Function of the GUI for LPC1768

In Figure 1.33, the scan interval and scan step can be

selected. Scan interval is the time between two sequential

scans. Scan step is the angle separation between two

sequential scans after steering the beam.

Figure 1.34: Scan Interval and Scan Step Definition

Two modes for the scanning are provided: Full scan and

Zone scan.

Figure 1.35: Scan Mode Selection

In Full Scan, this mode performs a full 360 degrees scanning

for all WiFi signals. The Scan Repeat is a parameter to

apply the rescanning for another round, up to 5 times,

default value is 1.

After clicking the Start button, the full scan will begin and a

bar shows the progress. While scanning, another window

near the “Reset” button is showing the current main beam

direction, as shown in Figure 1.36.

Figure 1.36: Status Bar and Current Main Beam Direction

When the scan finished, a popup table will show the WiFi

signals information in surrounding environment. For the

current four element linear antenna array, the main beam is

able to steer from -50º to +50º for WiFi application. The full

scan function has been modified to show only ±50º

directions.

Figure 1.37: Full Scan Results Using Four-Element Linear

Antenna Array

The table in Figure 1.37 presents the full scan results for the

four-element linear antenna array with the main beam

steering from -50º to +50º in the step of 10º. At each

direction, the table is displaying Main Beam Direction,

SSID, MAC Address, RSSI and Link Quality. It is clear that

along with the beam rotating, the RSSI and link quality are

showing different values.

In Zone Scan mode, it allows scanning a defined area or

zone by only steering the beam within this defined zone.

When the scan finishes, a popup table will show the WiFi

signals information within the selected area. The table

presented in Figure 1.38 shows the defined zone scan results

for the four-element linear antenna array with the main

beam steering from -

30º to +30º in the step of 10º.

Figure 1.38: Zone Scan Results Using Four-Element Linear

Antenna Array


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1.2.2.3.2 Best Signal Function

The second tab in the GUI is called Best WiFi, as

demonstrated in Figure 1.39. This function enables the user

to identify the best available WiFi signals at the location.

This is carrying out by fully steering the main beam to

enable the full scan the surround environment for the best

WiFi signals.

Figure 1.39: Best Signal Function of the GUI for LPC1768

After selecting the scan interval and scan step, the program

will automatically perform a full scan and accurate fine

tuning. Finally, the detailed best WiFi connect information

will be listed, which includes SSID, MAC Address, Signal

Strength and Link Quality.

Figure 1.40: Best Signal Scan Results Using Four-Element

Linear Antenna Array

1.2.2.3.2 Choose WiFi Function

In this function, the system allows the user to connect to the

desired WiFi network. The system will keep steering the

beam in order to keep the signal strength above the signal

threshold. In this mode, the user has to select the desired

WiFi network resulted from the pre- scanning, define the

first and second threshold and then start the scanning. The

system will automatically connect to the desired wireless

network while steering the main beam in the surround

environment in order to identify the direction of the best

signal strength. The function continues monitoring the

performance of the connected signal. If the signal drops below the first threshold, this will trigger the fine tuning

mode. If the system fails to recover it or the signal drop

below the second threshold, it will switch to the full scan

mode. The system will try to recover the WiFi network of

the best signal at all times. If the WiFi network is

unavailable, the system will display a warning message.

Figure 1.41: Choose WiFi Function of the GUI for

LPC1768

Figure 1.41 shows the Pre-scan. In this mode, the system is

capturing all WiFi networks (SSID) available to allow the

user to select the desired network.

Figure 1.42: Pre-Scan in Choose WiFi Function

The user is able to select a particular WiFi network from the

drop down list.

Figure 1.43: Threshold in Choose WiFi Function

Furthermore, it is able to setup the threshold values for the

chosen WiFi. In Figure 1.43, First Threshold will trigger the

fine tuning to take place in order to keep the signal strength

above the first threshold. Second Threshold will trigger the

full scan mode to search for the direction with the highest

signal strength for the chosen network. The first threshold

value is smaller than the second one. After setting up the


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parameters, the software program automatically performs a

full scan and accurate fine tuning. Finally, the detailed

chosen WiFi information will be listed, which includes

SSID, MAC Address, Signal Strength and Link Quality.

The system continues monitoring the RSSI using threshold

values to maintaining the strongest WiFi signal.

Figure 1.44: Choose WiFi Scan Results Using Four-

Element Linear Antenna Array

In the above Scanning, Best WiFi and Choose WiFi

functions, all of the algorithms are able to cover the main

beam steering from 0º to 360º. However, limited by the four

elements linear antenna array characterization, only -50º to

50º beam rotating is performed. Further research will

produce a wider scanning range smart antenna array to

generate more accurate scanning results.

2. RESULTS

This paper presents the software implementation to

automatically configure the smart antenna array system.

Two series of control systems are developed for

microprocessor PIC18F4550 and LPC1768, respectively.

For microcontroller PIC18F4550, research begins with a

virtual SPI communication algorithm between the microchip

and digital potentiometers. A graphical user interface has

been proposed to control the microchip through a laptop.

After initializing PIC18F4550, the GUI transfers the control

signal into a Microchip compiler called MPLAB and

changes the C code into a Hexadecimal (Hex) document. By

utilizing the Bootloader program, this Hex code will be

delivered into the microchip PIC18F4550 and then

configures the phase shifters on the smart antenna array.

Two control methods: Manual Control and Switching

Control are provided to achieve particular DC voltage or

square waveforms from the digital potentiometers. The

PIC18F4550 software control system is able to generally

configure the smart antenna array but requires other

application to check the WiFi signal variations.

Two improved versions of the GUI are developed for

microcontroller LPC1768. This microchip provides real time

control between a laptop which makes the GUI more

advanced. Both of the GUIs allow the user to detect SSID,

RSSI, MAC Address and Link Quality of WiFi signals

surrounding the laptop. The basic GUI can manually

configure the phase shifters and display all of the WiFi

information. By changing the phase shifters, it is able to

rotate the antenna array main beam direction in order to

analyze and monitor the received WiFi signals. Furthermore,

this chapter proposes a beta version of an advanced software

package for LPC1768, which demonstrates full scanning

and basic adaptive beamforming for WiFi signals.

1. The software control system is compatible with

Windows XP/Vista/7 and 8, with stable performance.

2. The virtual SPI algorithm is able to accurately configure

the digital potentiometers.

3. The GUI for PIC18F4550 is able to generate particular

DC voltages and square waveforms for the digital

potentiometers to control the smart antenna array.

4. A VB script is developed for PIC18F4550 to

achieve an automatic control between the microcontroller

and laptop.

5. Real time control is obtained for microprocessor

LPC1768 with steady connections.

6. The GUI for LPC1768 demonstrates Manual Control and

Automatic Control. Both of the GUI illustrate detailed

received WiFi information based on the smart antenna array

system

7. The advanced GUI using LPC1768 is able to perform an

automatic antenna beam steering and select a best WiFi

signal around the control terminal.

3. CONCLUSIONS AND FUTURE WORK

Several preliminary software programs to configure the

adaptive beamforming are explored in this paper. In the

developed smart antenna, a laptop running Windows is used

as a processing device and WiFi signals (2.45GHz) are

detected and evaluated. Using a microchip PIC18F4550, the

developed graphical user interface is able to manually send

various DC voltages and square waveforms to the phase

shifters. Moreover, the software programs investigated for

the microprocessor LPC1768 can achieve both of manual

control and automatic steering. In manual control, it is able

to send particular control voltages to the phase shifters and

observe the variation of WiFi signals detected by the array.

For automatic steering, some basic algorithms are

implemented and the software program could perform a full

scan first and then select the strongest WiFi signal direction

in the environment. This work demonstrates that the fully

integrated smart antenna can be applied for future mobile

applications.

Overall, it is concluded that the required adaptive antenna

performance can be achieved using the fully integrated

smart antenna systems. Therefore, it is possible to embed the


_______________________________________________________________________________________


complete smart antenna into future mobile devices in

wireless communication industry.

The future works of this research includes the transfer of

GUI into Android and IOS. This research presented several

prototype software programs to detect and analyze WiFi

signals using the proposed smart antenna in Windows.

Future work will continue to improve the control software

and also transfer the algorithms into Android and IOS

mobile operating systems.

4. REFERENCES

[1] http://www.microchip.com/.

[2] http://orwelldevcpp.blogspot.co.uk/.

[3] http://www.flashmagictool.com/.

[4] G. Wang, M. Romeo, C. Henderson, and J.

Papapolymerou, "Novel Reliable RF Capacitive MEMS

Switches With Photodefinable Metal-Oxide Dielectrics,"

Journal of Microelectromechanical Systems, vol. 16, pp.

550-555, 2007.

[5] HMC928LP5E Analog Phase Shifter, Hittite Microwave

Corporation.

[6] Y.-G. Kim, K. W. Kim, and Y.-K. Cho, "An ultra-

wideband microstrip-to-CPW transition," IEEE MTT-S

International Microwave Symposium Digest, pp. 1079-

1082, 15-20 June 2008.

[7] D. F. Filipovic, R. F. Bradley, and G. M. Rebeiz, "A

planar broadband balanced doubler using a novel balun

design," IEEE Microwave and Guided Wave Letters, vol. 4,

pp. 229-231, 1994.

[8] PIC18F4550 Data Sheet, Microchip Technology Inc,

2009. [131] LPC1768 Data Sheet, NXP Semiconductors,

2014.

[9] AD5290 Data Sheet, Analog Devices Inc. 2014.

[10] NJM2360 Data Sheet, New Japan Radio Co.Ltd. 2013.

[11] FT232R USB UART I.C. Data Sheet, Future

Technology Devices International Ltd. 2005.

BIOGRAPHIES

Aatish Gandotra, a student of Electronics

and Communication Engineering in his final

year with deep interest in telecommunication

and networking.

Publications :- 1. Replication of attacks in

wireless sensor network using NS2.

Tejaswi Singh, a student of computer

science engineering in his final year with a

knack for network security.

Publications :- 1. Replication of attacks in

wireless sensor network using NS2.

http://www.microchip.com/

http://orwelldevcpp.blogspot.co.uk/

http://www.flashmagictool.com/